Cosmological phase transitions in warped space: gravitational waves and collider signatures

Abstract

We study the electroweak phase transition within a 5D warped model including a scalar potential with an exponential behavior, and strong back-reaction over the metric, in the infrared. By means of a novel treatment of the superpotential formalism, we explore parameter regions that were previously inaccessible. We find that for large enough values of the t'Hooft parameter (e.g. N 25) the holographic phase transition occurs, and it can force the Higgs to undergo a first order electroweak phase transition, suitable for electroweak baryogenesis. The model exhibits gravitational waves and colliders signatures. It typically predicts a stochastic gravitational wave background observable both at the Laser Interferometer Space Antenna and at the Einstein Telescope. Moreover the radion tends to be heavy enough such that it evades current constraints, but may show up in future LHC runs.

On the maximal strength of a first-order electroweak phase transition and its gravitational wave signal

“…The conclusions from the analysis of Sections 4.1 and 4.2 may in principle be generalizable to other theories beyond the SM, with the notable exception of models with an approximate conformal symmetry, which include scenarios with a pseudo-Nambu-Goldstone boson associated with a spontaneously-broken approximate conformal symmetry [54][55][56][57][58] (see also [35,36,[59][60][61]) (dilaton-like) as well as models which feature classical scale invariance [14,62]. Focusing on the former (though the following discussion does also apply to the latter scenarios), the effective potential then contains a scale-invariant term multiplied by a function that varies weakly with the scale [119]:…”

Detecting gravitational waves from cosmological phase transitions with LISA: an update

“…It would then seem that plasma friction would play a negligible role on the expansion; however, for this to be the case, the amount of supercooling is typically required to be extremely large. To see this, we assume in the following that there is a relatively small number N of particles in the plasma that acquire a mass ∆m in the PT and produce transition radiation (notice that this is questionable in one of the prime examples -the holographic phase transition [28][29][30][31][32][33][34][35][36][37][38][39][40] -since there a large tower of particles will obtain a mass in the transition). The released energy is in this case of order ∆m 4 (or somewhat larger) and using (15) one finds that the Lorentz factor increases until it reaches the steady-state value…”

“…Five-dimensional warped models have attracted much attention in the literature as they provide a natural and well-motivated framework for a very strong first-order PT [28][29][30][31][32][33][34][35][36]39]. In the effective 4D language, this PT involves the radion scalar field whose potential stabilizes the interbrane distance determining the size of the slice of Anti-de Sitter space in Randall-Sundrum models.…”

“…In CH models, since the Higgs arises only when a non-zero condensate χ forms, the confinement PT and the EWPT are naturally linked. Nevertheless, until recently, past studies considered them separately, focusing either on the confinement PT, described by the dynamics of a dilaton/radion and relying on a 5D description [28][29][30][31][32][33][34][35][36]39] as discussed in the previous subsection, or assumed that the EWPT takes place after the confinement of the strongly-coupled sector [69,159,172,173]. The confinement PT is generically very strong, and is known to produce very large GW signals [29,32,39].…”

Dark, cold, and noisy: constraining secluded hidden sectors with gravitational waves

“…Strictly speaking, we should here distinguish between the temperature at which gravitational waves are emitted (usually referred to as T * ) and T nuc . The two temperatures may be different if the latent heat released during the phase transitions heats the plasma considerably compared to its initial temperature, as could be the case for instance for a phase transition happening during a vacuum-dominated epoch[5,[41][42][43][44][45][46][47][48][49][50][51][52]. However, in the following we will only consider phase transitions occurring during radiation domination, and we will therefore set T * = T nuc in the rest of this paper.…”